Rust-preventive coating

Abstract

A rust-preventive coating comprises two layers of coatings contacted with each other, wherein among the two layers of coatings, a first coating as a coating at an inner layer side is obtained from a first paint composition that contains a first metal-based powder and a first binder component, among the two layers of coatings, a second coating as a coating at an outer layer side is obtained from a second paint composition that contains a second metal-based powder and a second binder component, and compositions are different between the first metal-based powder and the second metal-based powder.

The invention claimed is: 
     
       1. A rust-preventive coating comprising a laminated body comprising two layers of coatings contacted with each other, wherein
 among the two layers of coatings, a first coating as a coating at an inner layer side is obtained from a first paint composition that contains a first metal-based powder and a first binder component, 
 among the two layers of coatings, a second coating as a coating at an outer layer side is obtained from a second paint composition that contains a second metal-based powder and a second binder component, and 
 the first metal-based powder comprises a first zinc-based powder comprising one or more selected from zinc powders and zinc alloy powders and a first aluminum-based powder, and 
 the second metal-based powder comprises: a second zinc-based powder comprising one or more selected from zinc powders and zinc alloy powders; and a second aluminum-based powder comprising one or more selected from aluminum powders and aluminum alloy powders, wherein 
 RL<RU≦2.7RL is satisfied where RL represents a first aluminum ratio as a mass ratio of the first aluminum-based powder to a total of the first zinc-based powder and the first aluminum-based powder of the first metal-based powder and RU represents a second aluminum ratio as a mass ratio of the second aluminum-based powder to a total of the second zinc-based powder and the second aluminum-based powder of the second metal-based powder. 
 
     
     
       2. The rust-preventive coating as set forth in  claim 1 , wherein the second aluminum ratio RU as the mass ratio of the second aluminum-based powder to whole of the second metal-based powder is less than 50 mass %. 
     
     
       3. The rust-preventive coating as set forth in  claim 1 , wherein at least one of the first metal-based powder and the second metal-based powder has a scale form. 
     
     
       4. The rust-preventive coating as set forth  claim 1 , wherein
 a contained amount of the first metal-based powder in the first paint composition is 20 mass % or more and 60 mass % or less, and 
 a contained amount of the second metal-based powder in the second paint composition is 20 mass % or more and 60 mass % or less. 
 
     
     
       5. The rust-preventive coating as set forth in  claim 1 , wherein at least one of the first binder component and the second binder component contains an inorganic binder component. 
     
     
       6. The rust-preventive coating as set forth in  claim 5 , wherein the inorganic binder component includes, on the basis of whole paint, 5 mass % or more and 40 mass % or less of an organic silicon compound and 0.05 mass % or more and 2 mass % or less of an organic titanate compound. 
     
     
       7. The rust-preventive coating as set forth in  claim 6 , wherein the organic silicon compound contained in the inorganic binder component comprises one or more compounds selected from the group consisting of tetraalkyl silicate compounds having an alkyl group which has one to three carbon atoms and oligomers thereof. 
     
     
       8. The rust-preventive coating as set forth in  claim 6 , wherein the organic titanate compound contained in the inorganic binder component comprises an organic compound represented by a general formula of Ti(X) 4  and an oligomer thereof, where X represents one or more functional groups selected from the group consisting of: alkoxy groups having one to four carbon atoms; chelating substituent groups; and hydroxyl group. 
     
     
       9. The rust-preventive coating as set forth in  claim 1 , wherein at least one of the first binder component and the second binder component contains an organic binder component. 
     
     
       10. The rust-preventive coating as set forth in  claim 1 , wherein at least one of the first paint composition and the second paint composition is a nonaqueous composition. 
     
     
       11. A rust-preventive member comprising the rust preventive coating as set forth in  claim 1  on a substrate. 
     
     
       12. The rust-preventive member as set forth in  claim 11 , further comprising an overcoat layer provided at outside the rust-preventive coating. 
     
     
       13. The rust-preventive coating as set forth  claim 1 , wherein 1.3RL≦RU≦2RL is satisfied.